FONT meeting notes October 6 2006
Present:
Hamid, Phil, Glenn, Tony (Oxford)
Christine (SLAC)
Alexander (DL)
0. New student
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Ben Constance has started and will join us at future meetings.
1. FONT test setup (Hamid, Glenn)
---------------------------------
The lab refurbishment is essentially finished modulo work on the fan.
Two new desks are on order.
Hamid has set up the signal generators but it looks tricky to implement
overall synchronisation with the external apparatus.
We can use the Agilent to simulate 3 short bunches, but it's not obvious
how to synchronise the 357MHz clock w.r.t. these. The 357MHz 'reference'
clock is at 10MHz, so one could imagine changing the clock frequency to
360MHz, an integer multiple of 10MHz, and phasing the bunches w.r.t the
10MHz, but this will need investigation and starts to get a bit baroque.
For now we will proceed with generating all the signals using the FPGA
itself, and feeding them back in. We'll continue to explore the 'external'
option for later.
Glenn reported another 'feature' in that we cannot easily change the
relative amplitude of the 3 bunch signals generated in this fashion, which
is annoying. It would be nice to be able to change the bunch signals to
mimic the action of the feedback and study performance.
Hamid said this COULD be done externally using the TTI but only special bunch
spacings are allowed: 133, 166 ... ns. By contrast the Agilent allows us to
change the bunch spacing but not the relative amplitudes! And there is still
the synchronisation issue.
In principle we could buy a fancy precision clock generator, budget permitting.
Stay tuned!
2. PCB BPM processors
---------------------
Hamid will agree with Colin the modifications needed to the PCB design.
we need to get the board order out ASAP. This is now getting critical.
We will load 5 boards.
** ACTION: HAMID/COLIN
3. FONT4 board programming
--------------------------
An update will be given next meeting.
4. Dates for November ATF visit
-------------------------------
Glenn, Hamid and Christine will go; Phil if possible; Alexander will not
go this time.
Probable interval: arrive 5,6,7 Nov, leave KEK 15,16,17 Nov.
Programme:
i) Timing, synchronisation and functionality of FONT4 board.
ii) test new BPM PCB processors
iii) housekeeping: verify cable plant, dress cables, setup Eel's bedroom.
Still to decide on whether setting up local PC is worth the effort.
Phil to discuss with stewart.
** ACTION: PHIL
5. Modelling of FESA data (Tony, Christine) - see file on www
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Tony submitted multiple seed runs to check the statistical variance of his
results. For 5000 e- in the beam and 11 runs he found 10%-level sigma on
the hits on each stripline. This is much smaller than the difference between
his results and Christine's.
Phil requested to see the resulting statistical variation on the BPM signal.
** ACTION: TONY
As a cross-check he ran GEANT with and without the low-energy shower mods.
He found 50% more hits with the low energy mods.
Christine *should* be using the same code, but will double check.
She will also run the 'vanilla' version to perform the same cross check as
Tony.
** ACTION: CHRISTINE
Christine has prepared a catalogue of all the July runs - thanks!
She checked the 'anomalous' run reported by Tony last week but could find
nothing obviously wrong in terms of a mislabelling of the beam conditions.
Tony will check the sensitivity of his results to proximity to the edge of
the test module aperture.
** ACTION: TONY
Alexander reiterated that the effect from secondary emission e- should be
'stronger' than that from those that pass straight through the BPM strip.
VERY low-energy e+- and photons could be important here: the photoelectric
effect! Tony will look into lowering the shower energy threshold even further,
down to 10eV?
Christine has had further discussion with Steve Smith, but we seem to be
reaching the point where we need to resort to a proper EM simulation of the
electrical signal induced on the striplines.
Tony reported that we have 1 week left on the evaluation copy of Particle
Studio. He will check how much the licence is.
Tony will also check out OPERA3D, as the Neutrino Factory group is interested
in this code and we may be able to piggy-back on a licence.
** ACTION: TONY
6. Next meeting
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Suggest *** Tuesday *** October 17, 08.00/16.00
best wishes,
Phil
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